Is the XML file still in the App_Data directory? What is its pubDate? If it is not there, then something obviously deleted it :-).

Also is it invisible when you are logged in? Or can you see it then? If you can see it, then it is a publish date issue. I have identified a bug (not a huge one, but a bug none the less) that will make the post not show until a lingering timezone offset is
corrected.... the joy's of using a beta release.